// 代码索引 3-3-1-1
#include <Eigen/Dense>
#include <iostream>
 
int main()
{
    Eigen::ArrayXXf  m(2,2);
    
    // assign some values coefficient by coefficient
    m(0,0) = 1.0; m(0,1) = 2.0;
    m(1,0) = 3.0; m(1,1) = m(0,1) + m(1,0);
    
    // print values to standard output
    std::cout << m << std::endl << std::endl;
    
    // using the comma-initializer is also allowed
    m << 1.0,2.0,
         3.0,4.0;
        
    // print values to standard output
    std::cout << m << std::endl;
}